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    Re: ex-meridian problem
    From: Bruce Stark
    Date: 2001 Feb 17, 3:54 PM

    Sometimes an experiment can help clarify things.
    Suppose our dead reckoning puts us about 30� N, 145� W. It's a little before
    noon. We get a true altitude of 69� 20'. The sun's declination is 10� N, his
    GHA 140�. With this data, using the Ex-meridian tables, we get a latitude of
    30� 8' north.
    But since we aren't sure of our DR longitude, we work the problem again using
    146� west. That gets a latitude of 29� 54'.
    Obviously, if we plotted this and drew a line from 30� 8' N, 145W to 29� 54'
    N, 146� W we'd have a chord of a circle. The sun's geographic position would
    be the center of the circle and his zenith distance the radius.

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